title: The uremic toxin indoxyl sulphate enhances macrophage response to LPS.
abstract: Indoxyl sulphate (IS) is a protein-bound uremic toxin that results from the metabolism of dietary tryptophan normally excreted by kidney through the proximal tubules. Thus the toxin accumulates in the blood of patients with impaired renal function such as in chronic kidney disease (CKD). High IS serum levels in patients with CKD suggest its involvement in CKD progression and in the onset of complications. Its presence in plasma is also a powerful predictor of overall and cardiovascular morbidity/mortality. IS is a well known nephrovascular toxin but very little is known regarding its effects on the immune system and in particular during inflammation. In this study we examined the effect of IS on macrophage activation in response to lipopolysaccharide from E. coli (LPS), a gram negative bacterial endotoxin associated with inflammation and septic shock. To simulate the uremic condition, J774A.1 macrophages were incubated with IS at concentrations observed in uremic patients (1000-62.5 µM) both alone and during LPS challenge. IS alone induced release of reactive oxygen species (ROS), through a mechanism involving pro- and anti-oxidant systems, and alteration in intracellular calcium homeostasis. When added to J774A.1 macrophages in presence of LPS, IS significantly increased the nitric oxide (NO) release, inducible nitric oxide synthase (iNOS) and cycloxygenase-2 (COX-2) expression. IS pre-treatment was also associated with an increase in tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) production by macrophages stimulated with LPS. Mechanistic studies revealed that IS increased LPS-induced NF-kB nuclear translocation, ROS release and altered calcium concentrations, mainly because of mitochondrial calcium overloading. Moreover also in primary mouse peritoneal macrophages IS enhances the inflammatory response to LPS increasing ROS, NO, iNOS, COX-2, TNF-α, IL-6 and NF-kB levels. This study provides evidences that IS stimulates macrophage function and enhances inflammatory reasponse associated with LPS, thus contributing to altered immune response dysfunctions observed in CKD.
authors.affiliation: Department of Pharmacy, School of Pharmacy, University of Salerno, Fisciano (SA), Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Adesso
authors.forename: Ada
authors.initials: A
authors.lastname: Popolo
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Bianco
authors.forename: Rosalinda
authors.initials: R
authors.lastname: Sorrentino
authors.forename: Aldo
authors.initials: A
authors.lastname: Pinto
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Autore
authors.forename: Stefania
authors.initials: S
authors.lastname: Marzocco
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D016207:Cytokines / Q000378:metabolism; D004926:Escherichia coli; D005260:Female; D006706:Homeostasis / Q000187:drug effects; D007200:Indican / Q000633:toxicity* / Q000652:urine; D008070:Lipopolysaccharides / Q000276:immunology*; D008262:Macrophage Activation / Q000187:drug effects* / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D051436:Renal Insufficiency, Chronic / Q000276:immunology* / Q000503:physiopathology
chemical_list: D016207:Cytokines; D008070:Lipopolysaccharides; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D007200:Indican; D002118:Calcium